Explosive cartridge unit



5, 1947. B. COUNTERMAN EXPLOSIVE CARTRIDGE UNIT Filed Aug. 4, 1943 FIG.

w I! I If! FIG. 4

FIG. 3

INVENTOR. l-MIIS B. Countcrrnam wua ($5 gwumg.

v AT TORN Patented Aug. 5, 1947 UNITED STATES EXPLOSIVE CARTRIDGE UNIT Lewis B. Counterman, Kenvil, N. 1., assignor to Hercules Powder Company, Wilmington, lDeL, a corporation of Delaware 3 Claims. 1

This invention relates to an improved explosive cartridge unit and more particularly to an explosive cartridge unit comprising a cartridge and a sleeve, each part having a lock-forming means adapted to be moved into locked relationship with each other in response to a force tending to move the parts from engaged to disengaged position, and to an assembly of these units.

In certain blasting work as, for example, in the seismograph blasting art, it is necessary to assemble a. number of explosive units in order to build up a charge sufficient in strength to serve the purpose for which it is to be employed. Many methods have been devised for accomplishing this assembly of units. Sleeves movable into frictional and telescopic engagement with adjacent pairs of cartridges have been used but the length of the assembly is limited by the holding power developed by any one sleeve through its frictional engagement with the cartridges. Spiral threads have been provided for both the cartridge and sleeve; however, the provision of a fast thread which is necessary in order to expedite assembly of the units, has the disadvantage of permitting the units to become disengaged when a column of any appreciable length is made up. It is desirable to obviate this disadvantage of the fast threads and still retain,all of their desirable features.

Therefore, it is an object of this invention to provide an explosive unit comprising a cartridge, a sleeve, and thread means carried by these parts adapted to permit free assembly of the units into threaded engagement with each other and to prevent separation of the units by automatic movement of the thread means into locked position with each other inresponse to an axially applied force.

Another object is to provide a rigid unitary assembly of explosive units, the cartridges of each unit being held in position by means of sleeves received in threaded engagement with adjacent cartridges, each cartridge being held against separation from the other by means of serrated threads carried by the cartridges and sleeves, the serrated threads being movable into serrated engagement with each other in response to a force tending to move the parts from engaged to dis engaged position.

Still another object is to provide an explosive unit comprising a cartridge, a sleeve,-and chipboard threads carried on the outsideand inside respectively of each of the parts, the edges of the threads being serrated and movable into serrated engagement with each other in response to a force tending to move the sleeve and cartridge from engaged to disengaged position.

Accordingly, the objects of this invention are realized by providing an explosive unit comprising a cartridge filled with explosive, a sleeve, and

' a chipboard thread spirally carried on the inside and outside of the sleeve and cartridge respectively, each thread having a common pitch and directed in a common direction and having the edges thereof serrated. The threads are relatively dimensioned with respect to each other to permit free-threading engagement of the sleeves with the cartridges.

Having now indicated in a general way the nature and purpose of this invention there follows a more detailed description of the preferred embodiments thereof, with reference being had to the accompanying drawing in which:

Fig. 1 is a view showing the sleeve and cartridge of an explosive unit in nearly full-threaded engagement; I

Fig. 2 i a. part sectional and part elevational view showing the cartridge of one unit in threaded engagement with the extended sleeve of another unit;

Fig. 3 is a sectional fragmentary view showing the cartridge thread in free-threading relationship to the threaded recess of the sleeve;

Fig. 4 is similar to Fig. 3 but showing the cartridge thread in serrated engagement with the sleeve thread.

Referring to the drawing, numerali indicate the cartridge and numeral 2, the sleeve of the explosive unit. These parts may be fabricated in any well known manner of any suitable material as, for example, paper, cardboard, metal, or plastic. Fabrication may be accomplished by assembling a number of individual parts as hereinafter to be explained or by mean of a. molding operation when plastics are being used.

The sleeve 2 may be formed from various parts by feeding a thread-forming strip 3 onto a mandrel or other suitable support (not shown) at a predetermined pitch to form a continuous thread-receiving recess 4. The strip 3 may be fed onto the mandrel to form the recess in such a way that the recess may spiral either from left to right throughout the sleeve or from right to left, the only effect produced being in the direction in which the sleeve is turned to assemble it with a cartridge. The strip is of such width as to be wound in an open layer, the space or recess 4 between adjacent sides of the strip being of such width as to accommodate the cartridge thread 5 in free-threading relationship hereinends of the sleeve so that the cartridge may be easily inserted into either of the smooth unthreaded ends of the sleeve.

The cartridge I may be of the usual paperwrapped type. The cartridge ma be formed by feeding a tube-forming strip (not shown) onto a, mandrel (not shown) to form a tubular body element upon which is fed a band 5 which forms the cartridge thread 5. The band may be fed into position in such a way as to form a thread which spirals either from left to right throughout the length of the cartridge or from right to left, the only effects produced being those described with respect to the sleeve. In every case the spiral direction in an assembly of sleeves and cartridges will be in a common direction. Preferably, the cartridge thread 5 terminates short of the ends of the cartridge so that entr of the cartridge into the smooth ends of the sleeve is facilitated.

Where paper-wrapped cartridges i and paper or cardboard sleeves 2 are employed, the threadforming bands 3 and 5 may be made of paper or cardboard of a substantial thickness commonly referred to as chipboard.

The cartridges I and sleeves 2 are provided with a fast or low pitched thread in order to save time during assembly of the units.

In order to overcome the tendency of the low pitched thread to slip and permit separation of certain of the units when a number of the units have been assembled and the assembly is being lowered into a vertical borehole, it has been discovered that serrations 1 formed on each side of the cartridge and sleeve threads will effectively eliminate all slippage between adjacent thread surfaces. The locking effect of the serrated threads when moved into serrated engagement as shown by Fig. 4 was tested using axially applied forces of 300 pounds and over. No signs of separation of one cartridge from another were observed up to the point where the assembly began to fail structurally. It is preferred to provide the sleeve and cartridge threads with serrations /64 of an inch deep, measured from the peak of one serration or notched portion to the trough of adjacent serrations, and {i of an inch Wide, measured from the peak of one serration to the peak of the next. It is preferred to form the serrations on each edge or side of the chipboard thread-forming strip for both the sleeve and the cartridge.

When one side of each of the sleeve and cartridge threads is serrated, assembly of the parts must be made in such a way as to position the serrated edges in adjacent relationship to each other. In order to do this, it is necessary to have two types of cartridges and sleeves, one type of which has serrations on one side of the threads and the other type of which has serrations on the other side of the threads. Serration on both edges of each thread eliminates this necessity. The thread-forming strips may be serrated by means of a pair of case-hardened steel cutting wheels (not shown) properly spaced and an idler roller (not shown) maintained in close adjustment with the cutters. The thread-forming strip is then fed to the serrating wheels where the roller maintains the strip in proper cutting relationship with the wheels.

The serrated thread receiving recess 4 is formed wide enough to receive the serrated cartridge thread 5 in free-threading or free-floating relationship. This free-threading arrangement of parts permits the cartridge l and sleeve 2 to be engaged with each other by merely twisting the two parts in opposite directions relative to each other. This free-threading relationship is clearly shown in Fig. 3.

When it is desired to assemble a number of the units into a charge of a predetermined strength, the units, the cartridge and sleeve of which are generally received in the field in coextensive relationship to each other, are adjusted so as to move the sleeve and cartridge out of substantial- 1y full engagement and into half engagement as shown by the sleeve and one cartridge of one unit of Fig. 2. Several units are extended in this manner. The extended units are then assembled by moving the exposed cartridge of one unit into the extended sleeve of another unit and so on until an assembly is built up of the desired length or explosive strength. It is preferred to have the sleeve and cartridge of each unit of the same length since in this way the cartridges may be joined together in a rigid manner due in part to the fact that the sleeves are in abutting end-toend relationship to each other forming a substantially continuous tubular reinforcing and joining member for the cartridges. However, sleeves of a length shorter than the cartridge may be used to join the cartridges together.

When the explosive column of assembled units is ready to be inserted into a borehole the column is moved to a vertical position and the weight of each cartridge is sufficient to set up a force throughout the column in response to which adjacent edges of the sleeve and cartridge threads move into serrated engagement with each other. This serrated engagement may also be brought about by means of an axial force set up in the column due to the movement of the sleeve into end-to-end abutting relationship to each other. In this way, the column is locked against separation before it is moved to a vertical position.

From the foregoing description, it is apparent that the objects of this invention havebeen accomplished by providing an explosive unit comprising a sleeve, a cartridge and serrated threads carried by the sleeve and cartridge, the threads of which are movable into serrated engagement with each other in response to an axially applied force and thereby locking each unit against separation from the other.

What I claim and desire to protect by Letters Patent is:

1. In an explosive device comprising a plurality of explosive units, each unit including a cartridge and a sleeve of substantially a common length, the cartridges being held in propagating relationship to each other by means of said sleeves extending across adjacent cartridge ends and forming a substantially continuous tubular 'reinforcing and joining member for said cartridges, the improvement comprising a, chipboard thread carried on the exterior of each of said cartridges, and a chipboard thread receiving recess formed in the interior of each of said sleeves, said cartridge threads being receivable in freethreadable relationship with said recesses, lockforming serrations carried by said threads and said recesses, said threads being slidable into serrated engagement with said recesses in response to a force tending to longitudinally pull the cartridge from the sleeve, whereby said cartridges are held in locked engagement with each other in said sleeves.

2. In an explosive device comprising a plurality of explosive units, each unit including a, cartridge and a sleeve of substantially a common length, the cartridges being held in propagating relationship to each other by means of said sleeves extending across adjacent cartridge ends and forming a substantially continuous tubular reinforcing and joining member for said cartridges, the improvement comprising a. chipboard thread carried on the exterior of each of said cartridges, and a. chipboard thread receiving recess formed in the interior of each of saidsleeves, said cartridge threads being receivable in free-threadable relationship with said recesses, lock-forming serrations formed on each side of said threads and said recesses, said threads being slidable into serrated engagement with said recesses in response to a force tending to longitudinally pull the cartridge from the sleeve, whereby said cartridges are held in locked engagement with each other in said sleeves.

3. In an explosive device comprising a, plurality of explosive units, each unit including a cartridge and a sleeve of substantially a common length, the cartridges being held in propagating relationship to each other by means of said reinforcing and joining member for said cartridges, the improvement comprising a chipboard thread carried =n the exterior of each of said cartridges, and a chipboard thread receiving recess formed in the interior of each of said sleeves, said cartridge threads being receivable in freethreadable relationship with said recesses, uniform lock-forming serrations formed on at least one side of said threads and on at least one adjacent side of said recesses, said threads being slidable into serrated engagement with said recesses in response to a force tending to longitudinally pull the cartridge from the sleeve, whereby said cartridges are held in locked engagement with each other in said sleeves.

LEWIS B. COUNTERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,317,354 Bennett Apr. 27, 1943 166,113 Kent July 27, 1875 524,895 Fulton s Aug. 21, 1894 705,420 Minges et ai. July 22, 1902 

